Research will be continued on a number of parameters that affect the transmission dynamics of LaCrosse (LAC) virus, both factors affecting vertical transmission of the virus through the egg of the vector mosquito, Aedes triseriatus, and factors affecting horizontal amplification through either vertebrated or venereal transmission by transovarially infected male mosquitos. Relative to vertical transmission, the effect of transovarial virus infection on the net replacement rate of vector females is being determined by quantifying vector female longevity and fecundity and juvenile stage mortality. Relative to venereal transmission, several aspects of male biology and field sampling techniques are being studied. Relative to vertebrate amplification, several aspects of vector female behavior are under study with current focus identification of bloodmeal sources of more than 300 wild females that obtained their bloodmeals under natural conditions. Identification is by enzyme-linked immunosorbant assay.